The present invention relates to swivel joints of the parallel or constant velocity type for transmitting torque between a drive shaft and a driven shaft. Such joints include an outer joint member connected with one of the shafts and an inner joint member connected with the other shaft. The outer joint member has a hollow cavity and the inner joint member is arranged within the cavity. The interior wall surface of the cavity has a first plurality of ball receiving grooves and the exterior surface of the inner joint member has a second plurality of ball receiving grooves equal in number to the first plurality. The plurality of grooves are arranged so that a ball for transmitting torque between the inner and outer joint members is carried between one pair of corresponding grooves. In this arrangement, the balls of each pair of grooves are subjected to a force caused by clearances or play which are a result of large manufacturing tolerances. This force tends to displace the balls out of their homokinetic plane in a direction causing a decrease in the angle formed by a plane containing the centers of the balls and the axis of rotation of the inner joint member. This type of joint also includes a cage having a plurality of circumferentially arranged window recesses, which is arranged between the inner and outer joint members, the balls being retained in the window recesses.
In such constant velocity, or parallel transmission joints, which are used in steering linkages for motor vehicles, manufacturing tolerances usually result in clearances which affect the steering control of the torque transmitting elements. As a result of such clearances, forces act on the torque transmitting elements displacing them out of a homokinetic plane detrimentally affecting the torque transmission capacity of the joint and its serviceable life. The adverse effects of such clearances become more significant when the inner joint member is deflected with respect to the outer joint member (i.e., when the axis of rotation of the inner joint member is angularly displaced relative to the axis of rotation of the outer joint member). Such adverse effects progressively increase even for a displacement angle of approximately 25.degree.-30.degree.. This is particularly true in joints which are provided with axially extending parallel ball receiving grooves, the balls carried between the grooves acting as the torque transmitting elements.
Further, one of the problems particularly found in motor vehicles is that considerable steering forces are required when operating the vehicle around corners, especially at very low speeds, or at very low tire pressures. In view of the modern trend towards the use of front-wheel drive vehicles, it has become customary to select a negative roll-radius for front wheel adjustment in order to ensure substantially straight forward movement of the vehicle even in situations of asymmetrical braking. However, such negative steering roll-radius also affects the general steering behavior of the vehicle since the wheels of the vehicle will not automatically return to a normal straight condition after tight cornering.
It is accordingly the principal object of the present invention to provide a swivel joint for a steering control linkage of the type having a cage for retaining ball torque transmitting elements, which can compensate for tilting movement of the cage as a result of play and clearances caused by manufacturing tolerances.
A further object of the present invention is to provide a swivel joint of the constant velocity or parallel type which has means for providing a restoring force effective during certain angular deflections of the joint, which force is either constantly effective on the joint or becomes effective when the angular displacement of the inner joint member with respect to the outer joint member reaches a certain predetermined angle.
Yet another object of the present invention is to provide a swivel joint having means to assist movement of the wheels to an original straight position after angular deflection of the joint caused by turning the wheels.
Other objects, features and advantages of the invention will become more apparent from the description of the invention in connection with the drawings to be described more fully hereinafter.